Gear-cutting machine.



T. FAWCUS.

GEAR CUTTING MACHINE.

APPLICATION FILED JUNE 14, 1912.

1,067,014. Patented July 8,1913.

aldl/w I QM. m W A 1 W GEAR-CUTTING MACHINE.

Specification of Letters Patent.

Patented July 8,1913.

Application filed June 14. 1912. Serial No. 703.721.

To all 'wizo'nz i t m (13/ concern Be it known that .l, THOMAS FAWFITS,a resident of Pittsburgh. in, the county of Allegheny and State oflennsylvmiia, have invented a new and useful improvement in GeauCuttinglllachines, of which the following is a full, clear, and. exactdescription, reference being bad. to the accompanying drawings, formingpart of this specilication, in which- Figure l is a side elevation of aportion of a gear-cutting machineembodying my invention; Fig. is 'afront elevation of a portion of the same; and ll 3 and l are detailviews.

My invention has relation to machines for cutting gears of the typecommonly known as double helical gears, and more particularly tomachines for this purpose of the general type described and claimed. inmy Patent No. 1,022,667, of April 9, 1912, in

which there are two cutting hobs arranged to act simultaneously upon agear blank, one hob cutting the portions of the double helical gear atone side of the peripheral center of the blank, and the other hobcutting teeth at the opposite side of such center, means being providedfor feeding both hobs in the same direction While cutting.

The present invention relates more especially to means of novelcharacter for feed ing the hobs or cutters to cause them to produce cutswhich are atreverse angles to the axis of the blank in which the cutsare being made.

Referring to the accompanying drawings, the numeral 2 designates the bedframe oi a machine; 3 designates a rotary blank-supporting table whichis mounted to rotate in a horizontal plane upon the vertical shaft 4,said shaft being mounted in a carriage 5, movable longitudinally on thebed of the machine A designates a partially cut blank which I have shownas rigidly'secured to the table 3, and which is to have double helicalteeth cut thereon. The beginnings of the two sets of teeth are indicaterespectively, at a and Z). The teeth a extend from the'upper edge of theblank'to the center line of the periphery and are cut by a rotary hob 7while the teeth b'extend from the lower edge of the blank to the center,and are out by the hob 8. These hobs may be, in general, of well knowncharacter, having helical cut ting teeth which mesh with the teeth whichthey cut in the blank. one of the bobs being made right *llilllllfil andthe other left handed and the two hobs being driven in oppositedirections. The hob T is mounted upon the transverse shaft 9, while thebob 8 is mounted 'on the transverse shaft 10, these two shafts beingjournaled one above another in suitable bearings on a vertically movableslide or earlier 11, which works in the vertical ways 12. Provision isalso made, by means of a member I?) adjustably mounted on the slide ll.whereby the bearings of the shaft l) may be adjusted to vary thedistance between the centers of the two shafts 9 and ll) to suitdifferent sized gear blanks.

The slide or carrier 11 is given its feed movement by the vertical screw14, which engages a nut portion 15 on the slide or carrier. l6designates suitable gearing for actuating the feed screw 14., and 17indicates suitable gearing for actuating a longitudinal shaft 18, bymeans of which the blank-supporting table 3 is rotated.

As thus far described, the machine does not differ essentially from thatshown and described in my patent above referred to and to whichreference may be had for a more complete description of the gearing andother operating parts. In cutting the double helical gears, it isapparent that the cutters must be in some way afi'ected relativcly tothe blank, in order-that the teeth a and b may be cut at the properreverse angles. vThe means specifically described for this purpose in mysaid patent consisted of a differential gearing whereby one of the hobsis driven at a speed relatively slower than that of the blank, while theother hob is driven at a speed relatively greater than that of theblank. The present invention does away with the use of dilterentialgearing or other gearing of a nature to change the speed of the hobsrelatively to that of the blank, and substitutes for such gearing meansof simple characterwhereby the hobs are moved endwise in reverse directions during the cutting operation To that end, the bearings for the hobshafts are mounted in the horizontal slidesil9 and 20.

The slide 19 is mounted in the member 13, while the slide 20 is mountedin the slide 11. Each of these slides 19 'andQQ-hasa nut portion, andthese -nut portions are engaged by the threaded shafts 21 and 22,respectively, these two shafts having threads of opposite hand, as shownin Fig. 3. Se-

cured to the end'of' each of these shafts is a spiral gear 23, each ofthese spiral gears meshing with a corresponding gear 24:, which ismounted to slide vertically .on a driving shaft 25. The gears 24 have aspline and groove Connection with shaft 25, so that as they are movedvertically thereon, they will be rotated, said shaft being driven by agear wheel 26, at its upper end, which meshes with a gear wheel 27 onthe screw shaft 14:.

It will be apparent that as the slide 11 is fed by the action of thescrew shaft 14, the threaded shafts 21 and 22 willjbe rotated throughthe gears 23 and 24 and the slides 19 and 20 will be moved endwise inreverse directions, thereby causing the hobs or cutters to be movedendwise in opposite directions to effect the desired angularity of theteeth a and 6.. By changing the ratio of the gears 26 and 27 ,the degreeof-angularity' of the teeth can be readily changed.

Each hob shaft 9 and 10 is driven by a worm wheel 28, which meshes witha worm 29, on a. vertical shaft 30. There are two of these verticalshafts, one at each side of the machine and driven through suitablegearing 31, which may be arranged as in my patent above referred to, theshafts 30 of the present application corresponding to the shafts 18 and21 of the said patent. By reason of the vertical feed movement-of theslide 11, it is necessary to make the worms 29 movable on the shafts 30,and to this end,

, they are provided with a key-and-groove connection with the shafts 30and are engaged by brackets 82, carried by the slide 11, so that theworms will be'moved in unison with saidslide. It is also necessary toprovide for transverse movement of the hob shafts, relatively to theworms29, and this is effected by spline-and-groove connections 33between the worms 28 and said shafts. The vertical movement of thespiral gears 24 on the shaft 25 is. effected by the brack: ets 34, thelower bracket is carried by the slide 11, and the upper bracket by themember 13, so that all of the parts carried by the member 13 will bemoved when the cutters ire adjusted toward or from each other. T

The operation is substantially the same as in the machine of my saidpatent. That is to say, the gear blank having been secured in place onthe table 3 and the hobs 7 and 8 adjusted to a distance apart aboutequal to one-half the width of face of the gear to be cut, the machineis set in motion, thereby causing the hobs and the blank to revolve attheir relative speeds, that is, at the ratio which the number of threadsin the hobs bears to' he number of teeth'to be cut in the blank. Theblank is now moved forward in cutting relation to the hobs, thisnoe'aoii forward movement of the carriage 5 con tinuing until therequired depth of cut is reached. The upper hob 7 is set to cut slightlybelow its center lineon the edge of the blank,-.and the hob 8 to cutapproximately'at the peripheral center of the blank. When the blank hasbeen thus fed and the cutting operation has progressed until therequired depth of cut is reached, the feed screw 14 is thrownintooperation, thereby simultaneously feeding both hobs or cuttersdownwardly, and through the gearing described, effecting a 7 slowreverse endwise movement of the two hob shafts and hobs-as the cuttingproceeds.

- The advantages of my invention consist mainly in the fact that iteliminates the use of difi'erential gearing, thereby not only greatlysimplifying the machine and reducing the number of gear wheels required,but also results in more accurate work, due to the fact that the lostmotion in the actuating gearing can be largely eliminated.

I do not, of course, limit my invention to use in connection withmachines of the specific character described and claimed in my saidpatent, since it is obviously applicable to all machines of that generaltype. It will also be obvious that instead of the particular meansdisclosed for effecting endwise movement of the hob slides, any othersuitable gearing may be employed, and that various other changes may bemade in the construction and arrangement of the various parts withoutdeparting from the spirit and scope of my invention as defined in thefeeding both hobs in the same direction, and

gearing whereby the feeding movement effects reverse endwise movementsof the two hobs, substantially as described.

3. In a machine for-cutting double helical gears, a right-hand and aleft-hand hob, and means for revolving said hobsin opposite directions,means for feeding them in the same direction, said hobs being arrangedto actsimultaneously upon a continuously revolving gear blank, and meansfor effecting endwise movement of the hobs during their feedingmovement, substantially as described. v

4-. In a machine for forming double helical gears, two rotary cutters,means for feeding said cutters 1n the same direction, and means scribed.

6. In a machine for cuttin double helical gears, a pair of rotary ho smounted on separate axes and arranged to act upon a continuouslyrevolving gear blank, meansfor feeding both hobs in the same directionin a line parallel to the axis of the blank, and means for effecting asimultaneous movement of the hobs in a'direction at substantially rightangles to their first named movement, substantially as described.

7. In a machine for cutting gears, two hobs revoluble in oppositedirections and arranged to act upon a continuously acting gear blank,nwans for feeding both hobs in the same direction, and means for movingthe hobs in opposite directions and perpendicularl to their feedingmovement, sub,- stantial y as described.

8. In a machine for cutting double helical gears, a pair of rotary hobsarranged to feed 1 1 approximately parallel with the axis of 'the blankbeing cut, and means for effecting a movement of the hobs in a directionperpendicular to the feeding movement, substantially as described.

In testimony whereof, I have hereunto set my hand. i

'THOMAS FAWCUS. WVitnesses:

GEO. B. BLEMLNG, Geo. H. PARMELEE.

